1. Field of the Invention
The invention relates to a device for damping vibrations of a bobbin holder in yarn cross-winding machines in which the bobbin is friction driven by a cylinder which guides the yarn or by a plain roller.
2. Description of the Prior Art
During winding of yarn onto bobbins by friction means that are driven by the thread drum guides, vibrations of the bobbins occur thus effecting an improper shape of the winding to be formed. Normally such vibrations increase with the diameter of the winding. In order to avoid such occurrences various types of pressing devices are employed in known machines and are arranged to press the bobbin down to the cylinder, thereby securing a compact winding, and simultaneously damping the vibrations of the bobbin.
The pressing device acting on the arm of the bobbin holder, known from the disclosure in the Polish Patent Specification No. 42,487, comprises two cooperating levers, one of which is provided with a guiding surface, the other being provided with a roller that is fitted on the end of the lever which rolls over the mentioned guiding surface. The levers are carried by the body of the bobbin holder which is fitted to the frame of the machine. To the free end of the lever which supports the guiding surface a pull spring is attached, the other end of which is secured to a pin fitted in the body of the holder. The bobbin held in arms of a swivel holder is clamped by a flat spring which acts on the holder arm. The vibrations of the holder are damped under the action of the friction force of the roller rolling over the guiding surface of the lever being pressed against the roller by the spring.
In said arrangement the force damping the vibrations is not constant, and it decreases as the diameter of the winding increases. Moreover the device is rather extended, as it comprises elements causing the pressing down of the bobbin to the cylinder, as well as elements clamping the bobbin in the arms of the holder.
Said disadvantages and inconveniences are eliminated by the device according to the present invention in which the same elements are utilized for clamping the bobbin in the holder, and for damping vibrations. Inside the shaft, a portion of which is tubular and upon which the bobbin holder is swingably supported, is seated a spring which acts on a slidable pin and urges it against a lever which forms one of the arms of the bobbin holder, its function being to cause clamping of the bobbin between that arm and the adjacent arm in the holder arms. The longer arm of the holder carries a friction insert, and, through the medium of the spring provided in the shaft, it is urged against the carrier thereby causing the friction force exerted to dampen the vibrations of the holder.
The device according to the invention is characterized by a simple and compact construction. Eliminating of the unnecessary elements which are known components of the hitherto applied arrangement reduces the weight of the device as well as consumption of materials. The constant pressure of the holder arm with the friction insert placed therein, independent of the diameter of the winding, provides a constant friction force damping the vibrations of the bobbin holder, said force being able to be adjusted.